Field of the Invention
The present invention relates to a backlight unit, and more particularly, to a backlight unit including a light source mounted on a side of a liquid crystal panel and a liquid crystal display (LCD) device including the same.
Discussion of the Related Art
A flat panel display (FPD) device is applied to various electronic devices such as portable phones, tablet personal computers (PCs), notebook computers, monitors, etc. Examples of the FPD device include liquid crystal display (LCD) devices, plasma display panel (PDP) devices, organic light emitting display devices, etc. Recently, electrophoretic display (EPD) devices are being widely used as one type of the FPD device.
In such FPD devices (hereinafter simply referred to as a display device), the LCD devices are being the most widely commercialized at present because the LCD devices are easily manufactured due to the advance of manufacturing technology and realize a drivability of a driver and a high-quality image.
Since the LCD devices are not self-emitting devices, the LCD devices include a backlight unit provided under a liquid crystal panel, and display an image by using light emitted from the backlight unit.
The LCD devices are categorized into an edge type and a direct type depending on an arrangement of a light source configuring the backlight unit.
FIG. 1 is an exemplary view illustrating a cross-sectional surface of a related art edge type LCD device, and FIG. 2 is an exemplary view illustrating a cross-sectional surface of a related art slim type LCD device. FIG. 3 is an exemplary view illustrating a periphery of a catching part in which light is leaked, in an optical sheet applied to the related art slim type LCD device, and is an exemplary view illustrating an optical sheet applied to the LCD device of FIG. 2.
As described above, LCD devices are categorized into the edge type, in which a light source is mounted on a side of a liquid crystal panel, and the direct type in which the light source is mounted on a bottom of the liquid crystal panel. In FIGS. 1 and 2, the related art edge type LCD device is illustrated.
As illustrated in FIG. 1, the related art edge type LCD device includes a guide panel 14, a light guide panel 12, a light source (not shown), an optical sheet 13, a cover bottom 16, a reflector 17, a liquid crystal panel 11, and a top case 15.
The liquid crystal panel 11 includes a lower substrate, an upper substrate, and a liquid crystal layer formed between the lower substrate and the upper substrate. An upper polarizing film is adhered to an upper end surface of the upper substrate, and a lower polarizing film is adhered to a lower end surface of the lower substrate. The liquid crystal panel 11 is disposed on the guide panel 14, and the optical sheet 13 is disposed under the liquid crystal panel 11.
The liquid crystal panel 11 is disposed at the guide panel 14. The guide panel 14 guides the light guide panel 15, the light source (not shown), and the optical sheet 13. In particular, the guide panel 14 covers an end of the optical sheet 13.
The optical sheet 13 transfers light, which is emitted from the light source (not shown) and travels toward the guide panel 14 through the light guide panel 12, in a direction vertical to a bottom of the liquid crystal panel 11.
The light guide panel 12 transfers the light, which is emitted and is incident from the light source (not shown), toward the liquid crystal panel 11.
The reflector 17 is adhered to a bottom of the light guide panel 12, and a side reflector 17a is adhered to a side of the light guide panel 12. Therefore, the light which reaches the bottom and side of the light guide panel 12 may be reflected toward the liquid crystal panel 11 by the reflector 17 and the side reflector 17a. 
The light source (not shown) may use a light emitting diode (LED).
In the related art edge type LCD device, as described above, the end of the optical sheet 13 is covered by the guide panel 14. That is, there is no gap between the guide panel 14 and the optical sheet 13. Therefore, the light is not leaked between guide panel 14 and the optical sheet 13, and thus, a quality of an image displayed by the LCD device is good.
However, in the related art slim type LCD device of FIG. 2 developed for a slim structure, the guide panel 24 is separated from the end of the optical sheet 23 by a certain interval.
As illustrated in FIG. 2, the related art slim type LCD device includes a cover bottom 26, a reflector 27, a light guide panel 22, an optical sheet 23, a panel 21, a guide panel 24, and a tempered glass 28. The optical sheet 23 is separated from the guide panel 24 by a certain interval.
Therefore, some of light (which is reflected by a pattern formed in the light guide panel 22, the reflector 27, or a side reflector 27a adhered to a side of the light guide panel 22) is leaked through a gap between the optical sheet 23 and the guide panel 24, and for this reason, a quality of an image displayed by the LCD device is degraded.
In particular, as illustrated in FIG. 3, light leakage or light bounce severely occurs at a periphery A of a catching part 23a of the optical sheet 23.
The catching part 23a is provided as at least two or more at the optical sheet 23 in order for the optical sheet 23 to be fixed to an inner side of the guide panel 24 and the cover bottom 26. The catching part 23a is caught on a catching jaw 29 which is formed at the cover bottom 26 or the guide panel 24, and thus, the optical sheet 23 is fixed to the inner side of the guide panel 24 and the cover bottom 26.
As described above, in the related art slim type LCD device, light leakage or light bounce occurs through the gap between the optical sheet 23 and the guide panel 24, and severely occurs at the periphery A of the catching part 23a which is formed at the optical sheet 23. Nevertheless, the related art LCD device does not include a structure which prevents the light leakage or the light bounce.